Airports in some of the United States were on high alert Friday after investigators found a suspicious package on a plane in the United Kingdom the night before, a law enforcement source with detailed knowledge of the investigation said.

The suspicious package, which contained a "manipulated" toner cartridge, tested negative for explosive material, the source said, but it led to heightened inspection of arriving cargo flights in Newark, New Jersey and Philadelphia, Pennsylvania and a UPS truck in New York.

Police also were investigating a suspicious package at the distribution center of an airport in East Midlands, in the United Kingdom, an airport spokesman said. Authorities said they could not immediately connect that investigation to the ones unfolding in New Jersey, New York and Pennsylvania.

We also need to be extremely alert to the possible threat via our seaports, and I’m not talking about just our major ports, either. Of course, the Coast Guard and the Customs Service are doing their jobs, but at the same time, state and local authorities must be called in…..and I’m sure they are, in most locales. It behooves us ALL to be alert to the danger.